Suction system for abrading tool

ABSTRACT

A work abrading tool having a suction system for withdrawing abraded particles from the work surface to a collection location. The suction system preferably includes a fan or fans driven by the motor of the abrading tool and producing a flow of air which partially or wholly creates the suction effect. For best results, the fan or fans and an aspirator coact to produce together the suction flow of air.

[ July 23, 1974 United States Patent [191 Hutchins FOREIGN PATENTS OR APPLICATIONS SUCTION SYSTEM FOR ABRADING TOOL 1,197,539 6/1959 France 51/170 T 1,016,153

[76] Inventor: Alma A. Hutchins, 49 N. Lotus Ave., Pasadena, Calif. 91107 Aug. 21, 1972 [21] Appl. No.: 282,340

TT O0 77 H 55 9/1957 Germany............. 428,280 8/1948 Italy 293,751 12/1953 [22] Filed:

Switzerland.......,........l::... 51/170 T [52] US. Cl. 51/170 T, 51/273 [51] Int. B24b 23/02, B24b 55/06 [58] Field of Search 51/170 R, 170 PT, 170 T, 51/170 TL, 170 EB, 170 MT, 273, 275, 356; 417/89,179, 198

to a collection location. The suction system preferably includes a fan or fans driven by the motor of the abrading tool and producing a flow of air which par- [56] References Cited UNITED STATES PATENTS tially or wholly creates the suction effect. For best re- D N sults, the fan or fans and an aspirator coact to produce e agy 51,273 X together the suction flow of air. 51/273 X 18 Claims, 6 Drawing Figures 1,958,354 5/1934 Stephens........,................ 2,000,930 5/1935 2,251,442 8/1941 Emmons....

2,764,852 10/1956 Emmons m e r/ H n in a 2X 5 v it fi 1111 1. I41 I w m d 8 s- 4. 1 l O y w 2 a ain .0 7 l s 4 i A n l SUCTION SYSTEM FOR ABRADING TOOL CROSSREFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION This invention relates to improved portable power actuated abrading tools, such as power sanders, grind- 1 ers, or the like.

In my above identified prior application, I have disclosed a portable power operated work abrading tool, which may function as a sander, grinder, or the like, and in which a suction system is provided for withdrawing from the vicinity of the work surface particles or dust abraded therefrom, and delivering those particles to a collection bag or other container in a manner preventing their escape into the atmosphere. The flow of suction air in the tools of that prior invention was preferably produced by an aspirator arrangement, in which a primary flow of air discharging from or associated with the motor of the abrading tool acted by aspirator action to induce a secondary flow of air for transporting the abraded particles.

SUMMARY OF THE INVENTION The present application discloses certain improvements in air suction systems for abrading tools, which improvements are designed to increase and maximize the suction effect, and otherwise improve the structure and functioning of the tools for certain purposes.

Some features of the invention relate to the provision of a fan which is driven by the motor of the tool and creates, or assists in creating, the suction flow of air. A known prior device has attempted to employ a fan for this purpose, but has positioned the fan at an inconvenient location axially beyond the motor in a direction away from the work, resulting in a very bulky and difficult to handle overall tool assembly, and one in which the suction effect is very inefficient and ineffective. 'In my present invention, the fan is preferably located axially between the driving motor and the power actuated head, shoe or other structure which carries the work abrading element. The fan can then produce a flow of air in very efficient proximity to the work surface to optimize the action in drawing abraded particles to the collection location.

As another feature of the invention, I find it desirable in some instances to employ both an aspirator and fan functioning in conjunction with one another to produce together an extremely effective combined air flow pattern for withdrawing the abraded particles from the work surface and carrying them to the collection location. Preferably, the fan is located to produce an initial movement of the particles from the work surface toward a predetermined point, and the aspirator is connected into the air flow path at that point to supplement the air moving effect. The aspirator may be energized by a primary flow of air coming from or associated with the motor of the tool. In one arrangement, the motor is driven by compressed air, and its discharge air functions as the primary stream to the aspirator,

while in another form of the invention the motor is driven electrically or by other means and has a cooling fan producing a flow of cooling air through the motor and to the aspirator as the primary stream for energizing the aspirator. When a second fan is employed in this manner, it is desirable that the cooling fan of the motor be driven at a speed faster than the speed of the previ- .ously discussed particle pick-up fan, so that the aspirator driven by the cooling fan will in fact move air at a rate faster than the particle pick up fan and sufficient to actually add to its air moving effect.

It is also contemplated that, in some instances, a motor cooling fan and an aspirator energized by the air from this fan may be utilized together, without an additional fan, to induce the flow of air from the work surface to a collection bag.

BRIEF DESCRIPTION OF THE DRAWING The above and other features and objects of the invention will be better understood from the following detailed description of the typical embodiments illustrated in the accompanying drawings, in which:

FIG. 1 is a partially axial sectional view and partially elevational view of afirst form of grinding or sanding tool constructed in accordance with the invention, with the sectional portion being taken on the line 1-1 of FIG. 4;

FIG. 2 is a view taken on line2-2 of FIG. 1;

FIG. 3 is a reduced perspective representation of the FIG. 1 tool;

FIG. 4 is a horizontal section taken essentially on line 44 of FIG. 1;

FIG. 5 is a view similar to FIG. 1, but showing a variational form of the invention; and

FIG. 6 shows fragmentarily a variation of the FIG. 5 arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The grinding or sanding tool 10 shown in FIGS. 1 through 4 is of a type having a body 11 with a handle portion 12 by which the tool is manipulated manually to bring a rotatively driven abrading disc 13 into contact with a work surface 14. The disc 13 is circular about and turns about the rotary axis 15 of the tool, and may be either a relatively thin sandpaper type abrasive material, or a somewhat thicker and stiffer abrasive element of the type commonly referred to as a grinding disc. In either event, the entire exposed undersurface of the disc is irregularized to function as an abrading element, and the disc preferably (though not necessarily) is sufficiently flexible to deform at one of its sides to the condition illustrated at 16 in FIG. 1. A circular backing disc 17 of substantially the same diameter as abrasive disc 13 backs up the abrasive disc and may be deformable as shown in FIG. 1 with the disc, but is sufficiently stifi to resiliently resist that deformation and press the abrasive material against the work surface 14, and to return the abrasive material and disc to a directly planar condition when out of contact with the work surface. The backing plate 17 may be formed of an appropriate fabric-reinforced resinous plastic material, such as a suitable phenolic. As seen in FIG. 1, both the abrasive discs 13 and backing plate 17 contain central circular apertures 18 for receiving a retaining nut or screw 19 by which these elements are secured to the rotary hub 20 driven by motor 21. Hub 20 may be shaped as shown, containing a downwardly facing central recess 22 within which nut 19 is receivable in a position'of attachment to a screw 23 which is rigidly secured to and projects from the hub. When nut 19 is tightened upwardly in FIG. 1, the inner circular edges of elements 13 and 17 are clamped by the nut upwardly against an annular shoulder 24 formed on hub 20 to tightly frictionally retain elements 13 and 17 and drive them rotatively with hub 20.

In the FIG. 1 form of the invention, motor 21 is an air-driven rotary motor, receiving compressed air from a supply source represented at 25 through a passage 26 in handle body 11-12, under the control of an on-off valve 27 actuated by a trigger 28. The motor may be of the well-known vane type, having a vaned rotor 29, within an outer motor housing or stator 30, and driven about axis 15 relative to the stator, with the rotor carrying the previously mentioned hub 20 at its lower end. The actuating air leaves stator 30 of the motor through an opening 31 formed in the bottom wall 32 of the stator, and as it leaves the motor is still at a pressure substantially above atmospheric pressure, capable of acting through an aspirator 33 to induce a secondary flow of air for carrying away particles abraded from the work surface.

Disposed about rotor 21 and the driven abrading disc 13 and backing plate 17, the body 11 of tool carries an essentially annular shroud 24, which acts to essentially enclose the space about and above the abrasive disc in a manner confining air and particles abraded from the work surface for withdrawal by suction from the vicinity of the work surface to a collection bag 35. This shroud may have a cylindrical upper portion 36 received about a correspondingly cylindrical lower portion 37 of body 11, and'suitably secured in fixed relation thereto, as by fasteners as represented at 38, or by forming the shroud to be a tight pressed friction fit on the housing. In extending downwardly from its point of connection to body 11, the shroud may first continue cylindrically at 39, centered about axis 15, and then progressively flare or curve generally radially outwardly to an increased diameter ultimately terminating in'a generally axially extending portion 41 having an edge 42 disposed about abrasive sheet 13. Except at the locationof a cutaway or opening 43 formed at the left side of the tool in FIG. 1, edge 42 is circularly continuous about axis 15, and spaced radially outwardly from the peripheral edges 143 of elements 13 and 17 to provide a gap 44 radially between edges 42 and 43 and I through which suction air can flow upwardly into the space 45 between the shroud and hub 20. As seen in FIG. 1, edge 42 may lie in a plane 46 disposed transversely of axis and approximately coincident with or spaced just slightly above the plane of the undersurface of abrasive sheet 13.

At the location 43, the shroud is cut away so that its The upper reduced diameter typically externally cylindrical portion 48 of rotor hub or shaft carries and rotatively drives an air moving fan 49, constructed and driven to create an upward flow of air through gap 44 and space 45 to aspirator 33. This fan 49 desirably takes the form of a centrifugal impeller, typically a blower of the squirrel cage type, which may be stamped from a single annular piece of sheet metal appropriately deformed to form a series of circularly spaced radially extending vanes or impeller blades 50 acting to take suction from the annular space 51 at the radially innersides of the blades and blow the air centrifugally radially outwardly to discharge the air from the radially outer edges 52 of the blades. The impeller 49 may have an innerannular mounting portion 53, which is appropriately rigidly attached to hub or shaft 20, as by fasteners, brazing or welding, or by forming portion 53 as a tight pressed fit on the shaft.

The fan or blower 49 is contained within an annular compartment 54 formed in the shroud at a location spaced beneath the lower annular edge or end 55. of body 11, and beneath bottom wall 32 of the motor stator. This compartment 54 may be formed by providing an annular transverse wall or partition 56 in the shroud, welded or otherwise secured at its periphery 57 to the shroud, and having an inner edge 58 received in close proximity to the outer surface of hub 20. The underside of compartment 54 may be formed by a similar transverse annular wall59 peripherally secured to and projecting inwardly from the shroud and having an inner edge 60 which is spaced from the hub sufficiently to provide an annular gap 61 through which air may pass upwardly to the radially inner side of the, centrifugal blower 49. V

The air discharged centrifugally from fan 49 is blown into a discharge tube 62, which is connected tangentially to the shroud as seen in FIG. 2 for most effective flow of the air into tube 62. From tube 62, the air discharges into a hose 63, which is flexible and leads the air and carried abraded particles to the collection bag 35, which is porous to pass the air through the bag to its exterior while functioning as a filter retaining the abraded particles in the bag as in a conventional vacuum cleaner.

The flow of air produced by blower 49 upwardly within the shroud and then into tube 62 may be sufficiently rapid to, by itself, very effectively transport all of the abraded particles from the work surface to bag 35. However, this effect is desirably enhanced by the action of aspirator 33, which utilizes the energy remaining in the air discharging from motor 21 to further increase the rate of flow of the air leaving the fan. For this purpose, the air from the motor is conducted through a central tube 64 of the aspirator, to discharge from the end 65 of that tube located concentrically within previously mentioned tube 62, with the air from tube 65 discharging rightwardly at a rate of flow substantially greater than the rate at which air would flow in the surrounding space 66 under the influence of blower 49 in the absence of any aspirator action. Thus, the more rapidly flowing air discharging from tube 64 acts by aspirator action to increase the rate of flow of the air and abraded particles from fan 49, to thus boost or enhance the suction action and coact with blower 49 in assuring very effective and rapid delivery of all abraded particles to bag 35.

To recapitulate the manner of use of the tool of FIGS. 1 to 4, assume that the tool has been connected to the source of compressed air 25, and that discs 13 and 17 have been connected to hub 20 as shown in portion 12, actuates trigger 28 to commence rotation of rotor 29 and its shaft 48 and carried blower 49, and moves disc 13 to a position such as that shown in FIG. 1 in which it engages'work surface 14 at the location of cutaway 43 in the shroud. The exposed edge portion of disc 13 is pressed against the work surface with sufficient force to assure an effective abrading action, thus deforming the disc to the position shown in FIG. 1. As the tool is utilized in this manner, particles abraded from the work surface are drawn upwardly through space 44 about the periphery of disc 13, and are drawn inwardly through cutaway 43, to the radiallyinner suction side of blower 49, to be discharged therefrom through tube 62 and hose 63 to bag 35. The air exhausted from motor 21 acts through aspirator 33 to increase the rate of flow of the air and particles through tube 62and hose 63, as discussed. It is contemplated that shroud 34 may be formed of a somewhat flexible material, if desired, but in many instances is preferably substantially rigid, typically formed of a suitable rigid metal or an appropriate rigid fire repellent resinous plastic materiaLIt is also contemplated that in some instances the shroud may be circularly continuous at its 1 loweredge, rather thanbeing cut away at 43, in which event the entire annular undersurface of disc 13 is directly contacted with the work surface, without deformation of its edge in the FIG. 1 manner. Nut 19 is in either case desirably so shaped as to have its undersurface spaced or recessed upwardly above the level of the abrasive sheet, as shown, to avoid contact of the nut with the work surface.

FIG. 5 is a view similar to FIG. 1, but showing a variational arrangement in which an electric motor 21a is substituted for the pneumatic motor 21 of the first form of the invention. This electric motor may be controlled by a'trigger 28a on handle portion 12a of body 11a. The abrasive disc 13a, backing plate 17a, drive hub 20a, shroud 34a, centrifugal blower 49a, and aspirator 33a may all be substantiallythe same as the corresponding parts of FIG. 1.

, The electric motor 21a has a rotor represented somewhat diagrammatically at 29a, which turns about axis a relative to a diagrammatically represented stator 30a of the motor. The rotor 29a drives a downwardly projecting shaft 67 which may drive the abrasive carryabout axis 15a at a speed substantially slower than the speed of rotation of motor shaft 67. Above reduction gear assembly 68, motor shaft 67 rigidly carries and drives a desirably axial flow fan 69, which acts as a cooling fan for producing a flow of cooling air axially through the interior of the motor, and more specifically between and in direct cooling contact with both the rotor and stator, in a manner carrying away heat developed by the stator and rotor coils, bearings, etc. in operation. This flow of cooling air may enter the upper end of the motor through openings 70 formed in the top of body or housing 11a, and flows axially downwardly through the motor and fan, to be discharged downwardly by the fan into a space 71. From this space, the air discharges into the previously mentioned inner tube 64a of the aspirator. Because of the increased rate of rotation of fan 69 as compared with fan 49a, the rate of flow of air from tube 640 is desirably considerably greater than the rate at which the air about that tube would flow solely as a result of the action of fan 49a, so that the primary flow of air from tube 64a has the desired aspirator effectof inducing an increased rate of movement of the air stream carrying the abraded particles, as was the case in the first form of the invention.

FIG. 6 illustrates fragrnentarily another variation which may be the same as that of FIG. 5 except that the fan 49a and the compartment wall beneath it are omitted so that the aspirator action of the flow of air from the upper fan 69b serves by itself to produce the entire suction action, for withdrawing particles upwardly by suction from the work surface and through the shroud and aspirator to a collection bag such as that shown at 35 in FIG. 1. It is also to be understood that, if desired, thefan 69 but not fan 49a may in some cases be omitted from the FIG. 5 arrangement, in which case the fan 49a mayfunction alone as the air and particle displacing force, for producing the entire movement of air and particles from the work surface to the collection bag. In that instance, the inner tube 64a of the aspirator 33a of FIG. 5 may be omitted, so that only a simple air and particle discharge tube is provided at the location of the aspirator; or alternatively the flow of air from fan 49a could be employed in the aspirator 31 to produce by aspirator action a flow of cooling air through the motor. a

While certain specific embodiments of the present invention have been disclosed as typicahthe invention is of course not limited to these particular forms, but rather is applicable broadly to all such variations as fall within the scope of the appended claims.

I claim:.

1. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, a container for receiving and collecting particles abraded from the work surface, a fan located essentially between said motor and said unit and driven rotatively by said motor and constructed to produce a first flow of air moving particles abraded from said work surface toward said container for collection therein, a second fan located essentially between. said first fan and said motor and producing a second flow of cooling air through the motor and merging with said first flow of air produced by said first fan, and a speed reduction unit between said motor and said first fan driving the first fan and said first mentioned unit as a speed slower than the motor and said second fan.

2. A portable abrading tool as recited in claim 1, in- I cluding a shroud extending at least partially about said first mentioned unit and confining said abraded particles for flow to said container, and an aspirator in which said second flow of air induces movement of said abraded particles from said first flow of air toward said container.

3. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, and suction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, said motor being driven by compressed air and discharging air to said aspirator to induce movement of said particles.

4. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, suction means for withdrawing by suctionv rator action a secondary flow of air containing said particles. I I

5. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, andsuction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, saidfan being near said unit and producing an initial movement of said particles from near the work surface, and discharging a flow of air containing said particles to said aspirator.

6. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, and suction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, said unit being an essentially circular backing member driven rotatively by said motor about a predetermined axis and adaptedto carry an abrasive disc disposed transversely of said axis, said fan being driven rotatively about said axis with said backing member and acting to draw air and abraded particles by suction from the work surface, a shroud extending at least partially about said backing member to confine said particles, said motor having a flow of air passing therethrough and discharging to said aspirator as a primary stream through the aspirator, and means conducting air and particles discharged from said fan to the aspirator as a secondary stream so that said primary stream assists in inducing movement of the particles.

7. A portable abrading tool as recited in claim 6, in which said motor is driven by compressed air and discharges said compressed air at superatmospheric pressure as said primary stream to the aspirator.

8. A portable abrading tool as recited in claim 6, in which said motor is an electric motor, there being a second fan driven by said motor and producing said flow of air through the motor as a cooling stream, and discharging said cooling air to said aspirator.

9. A portable abrading tool comprising a body, a unit movable relative to said body to abrade a work surface, a motor for moving said unit to abrade the work surface, an aspirator, means defining a first path along which a first stream of air and entrained particles abraded from the work surface flow to said aspirator, means defining a second path along which a second stream of air passes in isolation from said first stream to merge therewith at the aspirator, a fan at a location along one of said paths driven by said motor and acting against the air of one of said streams, but not the other, upstream of said aspirator and discharging air along said one path to the aspirator, and a container to which the air of both of said streams flows, together with said particles after leaving said aspirator. 1

10. A portable abrading tool as recited in claim 9, in which said fan is located along said first path and discharges said first stream of air and entrained particles to the aspirator.

11.-A portable abrading tool as recited in claim 9, in which said fan is located along said second path and discharges air to said aspirator in a relation inducing movement of air along said first path by. aspirator action. 1

.12. A portable abrading tool as recited in claim 9, in-

cluding a second fan driven by said motor at a location along the other of said paths and discharging air therealong to said aspirator. 13.'A portable abrading tool as recited in claim 9, in which said motor is driven by compressed air and discharges air at superatmospheric pressure along said second path to said aspirator, said fan .being located along said first path.

14. A portable abrading tool as recited in claim 9, in which said second stream of air flows through said motor, to cool it, before reaching said aspirator.

15. A portable abrading tool as recited in claim 9, in which said unit is an essentially circular backing member adapted to carry a disc of abrasive material'and driven rotatively about a predetermined axis perpendicular to said backing member and discby said motor,

said fan being located axially between said motor and said backing member and being driven rotatively about said axis of the backing member.

1 6. A portable abrading tool as recited in claim 9, including a shroud extending at least partially about and at least partially enclosing said unit for confining said abraded particles to flow toward said container.

17. A portable abrading tool comprising a body, an essentially circular unit mounted for movement relative to said body to abrade a work surface, a motor for driving said essentially circular unit rotatively relative to said body about a predetermined axis, suction means for producing a partial vacuum acting to withdrawair and abraded particles by suction from near the work surface, and a shroud extending about a major portion of said unit and projecting to a location closely proximate said work surface and about said rotary unit and defining a space from which said suction means withdraw air and abraded particles, said shroud having an opening at one side of the axis of said unit through which a portion of said unit projects for contact with the work surface, said unit including a circular backing member adapted to removably carry an abrasive disc and adapted to flex locally with the disc, at the location at which said unit projects outwardly through said opening in the flange, and in a direction generally toward said motor and to a position of substantial angularity with respect to the remainder of said backing member and disc, without contact with or interference by the shroud.

18. A portable abrading tool as recited in claim 17, in which said shroud has a peripheral edge extending essentially circularly about and spaced from the periphery of said circular unit and lying essentially in a predetermined plane along the major portion of the circular extent of said edge but curving essentially arcuately away from said plane at the location of said opening in the shroud to form said opening. 

1. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, a container for receiving and collecting particles abraded from the work surface, a fan located essentially between said motor and said unit and driven rotatively by said motor and constructed to produce a first flow of air moving particles abraded from said work surface toward said container for collection therein, a second fan located essentially between said first fan and said motor and producing a second flow of cooling air through the motor and merging with said first flow of air produced by said first fan, and a speed reduction unit between said motor and said first fan driving the first fan and said first mentioned unit as a speed slower than the motor and said second fan.
 2. A portable abrading tool as recited in claim 1, including a shroud extending at least partially about said first mentioned unit and confining said abraded particles for flow to said container, and an aspirator in which said second flow of air induces movement of said abraded particles from said first flow of air toward said container.
 3. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, and suction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, said motor being driven by compressed air and discharging air to said aspirator to induce movement of said particles.
 4. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, suction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, said motor being an electric motor, and a second fan driven by said motor and producing a flow of cooling air therethrough and then to said aspirator for inducing by aspirator action a secondary flow of air containing said particles.
 5. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, and suction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, said fan being near said unit and producing an initial movement of said particles from near the work surface, and discharging a flow of air containing said particles to said aspirator.
 6. A portable abrading tool comprising a body, a unit mounted for movement relative to said body to abrade a work surface, a motor for driving said unit relative to said body, and suction means for withdrawing by suction from the vicinity of the work surface air and particles abraded from said surface, said suction means including an aspirator and a fan driven by said motor, said unit being an essentially circular backing member driven rotatively by said motor about a predetermined axis and adapted to carry an abrasive disc disposed transversely of said axis, said fan being driven rotatively about said axis with said backing member and acting to draw air and abraded particles by suction from the work surface, a shroud extending at least partially about said backing member to confine said particles, said motor having a flow of air passing therethrough and discharging to said aspirator as a primary stream through the aspirator, and means conducting air and particles discharged from said fan to the aspirator as a secondary stream so that said primary stream assists in inducing movement of the particles.
 7. A portable abrading tool as recited in claim 6, in which said motor is driven by compressed air and discharges said compressed air at superatmospheric pressure as said primary stream to the aspirator.
 8. A portable abrading tool as recited in claim 6, in which said motor is an electric motor, there being a second fan driven by said motor and producing said flow of air through the motor as a cooling stream, and discharging said cooling air to said aspirator.
 9. A portable abrading tool comprising a body, a unit movable relative to said body to abrade a work surface, a motor for moving said unit to abrade the work surface, an aspirator, means defining a first path along which a first stream of air and entrained particles abraded from the work surface flow to said aspirator, means defining a second path along which a second stream of air passes in isolation from said first stream to merge therewith at the aspirator, a fan at a location along one of said paths driven by said motor and acting against the air of one of said streams, but not the other, upstream of said aspirator and discharging air along said one path to the aspirator, and a container to which the air of both of said streams flows, together with said particles after leaving said aspirator.
 10. A portable abrading tool as recited in claim 9, in which said fan is located along said first path and discharges said first stream of air and entrained particles to the aspirator.
 11. A portable abrading tool as recited in claim 9, in which said fan is located along said second path and discharges air to said aspirator in a relation inducing movement of air along said first path by aspirator action.
 12. A portable abrading tool as recited in claim 9, including a second fan driven by said motor at a location along the other of said paths and discharging air therealong to said aspirator.
 13. A portable abrading tool as recited in claim 9, in which said motor is driven by compressed air and discharges air at superatmospheric pressure along said second path to said aspirator, said fan being located along said first path.
 14. A portable abrading tool as recited in claim 9, in which said second stream of air flows through said motor, to cool it, before reaching said aspirator.
 15. A portable abrading tool as recited in claim 9, in which said unit is an essentially circular backing member adapted to carry a disc of abrasive material and driven rotatively about a predetermined axis perpendicular to said backing member and disc by said motor, said fan being located axially between said motor and said backing member and being driven rotatively about said axis of the backing member.
 16. A portable abrading tool as recited in claim 9, including a shroud extending at least partially about and at least partially enclosing said unit for confining said abraded particles to flow toward said container.
 17. A portable abrading tool comprising a body, an essentially circular unit mounted for movement relative to said body to abrade a work surface, a motor for driving said essentially circular unit rotatively relative to said body about a predetermined axis, suction means for producing a partial vacuum acting to withdraw air and abraded particles by suction from near the work surface, and a shroud extending about a major portion of said unit and projecting to a location closely proximate said work surface and about said rotary unit and defining a space from which said suction means withdraw air and abraded particles, said shroud having an opening at one side of the axis of said unit through which a portion of said unit projects for contact with the work surface, said unit including a circular backing member adapted to removably carry an abrasive disc and adapted to flex locally with the disc, at the location at which said unit projects outwardly through said opening in the flange, and in a direction generally toward said motor and to a position of substantial angularity with respect to the remaindeR of said backing member and disc, without contact with or interference by the shroud.
 18. A portable abrading tool as recited in claim 17, in which said shroud has a peripheral edge extending essentially circularly about and spaced from the periphery of said circular unit and lying essentially in a predetermined plane along the major portion of the circular extent of said edge but curving essentially arcuately away from said plane at the location of said opening in the shroud to form said opening. 